Today, through advancements in nutritional science, we know more precisely what goes on inside the cow. That gives us the opportunity to manage the smaller pieces of the nutrition puzzle – protein fractions instead of crude protein – and to build a more precise diet to optimize cow health and performance.
We are just scratching the surface in some of these new areas of understanding, but the opportunity it gives us is truly amazing compared to just a few years ago. In order to step up the nutrition for your cows and be more precise in our ration formulation, we must first understand the basics of several key nutrients.
Protein, fiber, starch and fat are four principal elements of nutrition that create the foundation of dairy rations. Now that we understand more precisely what goes on inside the cow, many of the old rules of thumb for evaluating feedstuffs no longer apply.
Today, we have new and more refined rules of thumb that help us better evaluate the availability, use and ultimately the value of protein, fiber, starch and fat levels to the cow. And it all starts with analyzing your forages.
Crude protein is no longer king.
When looking at the nutritional analysis of a forage sample, we need to focus on the numbers that help us manage the protein fractions in the ration and minimize crude protein. The amount of ammonia present in the forage sample tells us a lot about how well or poorly that feed fermented and how much of an energy discount we will need to apply as that forage is fed out.
For example, when the ammonia content of forages is too high and exceeds the ruminal needs of the cow, she must excrete it, and that takes extra energy. Energy used for nitrogen removal cannot be used for milk production or maintenance requirements. Excessive ammonia in forages also reduces the more useful fermentable nutrients of those feedstuffs.
We also need to know how much of the protein belongs to other protein pools that are quickly or slowly degradable in the rumen, or perhaps only digestible in the small intestine. Understanding the rate and extent of protein digestibility helps to predict how much metabolizable protein will be supplied to the cow and therefore available for milk and milk protein production.
The amount of forage we can feed is directly proportional to the quality and quantity of the forages we have available. That means we must know the specific needs of groups of cows so the forage we feed them is tailored to their needs.
Recent work has increased our understanding of neutral detergent fiber digestibility (NDFd) and indigestible NDF or uNDF. Forage samples should no longer be evaluated on just how much acid detergent fiber (ADF) and NDF they contain. Today, we need to know NDF digestibility at different time points and uNDF in order to more precisely evaluate the fiber’s value in the diet and understand the potential energy contribution of that feedstuff.
Starch as a percent of dry matter has been an important number in forage analysis for years. However, it used to be that we only looked at starch content. Now we want to know how degradable that starch is and how quickly it will ferment in the rumen. Sometimes the cows don’t need more starch; they need a more highly degradable starch. It is all about tailoring your rations to meet specific cow needs.
For example, starch degradability is especially important for fresh cows. Newly fresh cows have a low dry matter intake, but they need a certain amount of starch and fiber to manage glucose demand and stay healthy.
Everything we add to the fresh cow diet takes up space, including starch sources. But not all starches have the same level of degradability. So including more quickly degradable starches in the fresh cow diet allows us to reduce total dietary starch and tailor the diet to better meet their needs and get them off to a good start.
Many types of fat are available, but not all fats are created equally. The cow uses each type of fat a little differently. Therefore, the different fats must be balanced with what the cow needs.
We are in our infancy of understanding all of the different fatty acids, but we do know that we have to balance the different types of fatty acids in the diet and use the right ones to target the response needed in the cow. Our goal should always be to manage energy balance and milkfat production – not to let milkfat production manage us.
For example, research has shown that Omega 3 fatty acids fed to fresh cows can increase milk production. Additionally, research demonstrates that C16:0 fatty acids can have a positive effect on butterfat production.
However, certain unsaturated fatty acids fed at excessive levels or in combination with higher-starch diets can depress milkfat production. It should be noted that the fat content of corn silage and other corn products is highly unsaturated.
Putting it all together
Dairy nutrition is really becoming precision nutrition. Once we have the basics down, these four elements of nutrition – protein, fiber, starch and fat – and we apply the new rules of thumb, we can focus on maximizing metabolizable energy and metabolizable protein in order to make more milk, more milk components and have healthier cows.
When we evaluate forages using these new approaches, it provides more insight into how available the nutrients are to the cows, how they will respond and what we need to buy or fill in with to meet all of their nutritional requirements.
At what level of production is it appropriate to explore some of the newer technologies like fatty acids and supplemental amino acids? This will vary by herd, but generally speaking, for healthy cows on a good forage base with limited environmental obstacles, herd managers have a great opportunity to use these technologies when the herd average is 80 pounds of milk or more.
For herds that are not ready to balance for lysine and methionine, or explore fatty acid balancing, there is still significant benefit to examining the rumen availability of dietary starch and fiber.
What is the future of dairy nutrition? We are probably headed to a world where we don’t balance on crude protein at all except to minimize it. And even metabolizable protein could become less important than balancing for the essential amino acids.
While we work toward that exciting future, we should stay focused on doing a good job optimizing the four key elements of nutrition so cows can maximize rumen function, make microbial protein and stay healthy and productive. Not only will that reduce cost, it also makes good environmental sense. PD
- Technical Services Specialist – Dairy Nutrition
- Purina Animal Nutrition
- Email Jeff Tikofsky